Replication comes in three varieties: local, asynchronous remote, and synchronous remote. Local replication keeps two local volumes synchronized with the same set of files. Asynchronous remote replication is typically done over an IP network connection, synchronizing data between a local and a remote volume at specific intervals. Synchronous remote replication typically keeps a local and a remote volume synchronized at all times. Due to the relatively high bandwidth required for synchronous replication, it is typically done via long-distance FC rather than via an IP connection.
Snapshots are point-in-time replicas that are made to use for backups of open files. A snapshot can be made very quickly, and it reflects the state of all data at the time of the snapshot. Because a snapshot is static, a tape backup can then be made from the snapshot without worrying about open files.
Thin provisioning allows for the creation of volumes that can be expanded without deleting the old partition and creating a new one. Thin provisioning can also save considerable storage because it allows for the creation of a relatively small partition that can be grown whenever it gets close to being full.
Tiered storage is used to set up policies that keep critical data on the fastest storage. Typically, first-tier storage uses 15,000 rpm (15K) FC drives, second tier uses 10,000 rpm (10K) FC, and third tier uses 7,200 rpm (7.2K) FC. The fourth tier likely consists of the much less expensive SATA-based storage, which can be up to 10 times cheaper than FC drives. Xiotech offers an even faster first tier with its optional SSD (solid state disk) drives; SSD drives are very, very high performance but also very expensive and low capacity (6GB).
Virtualization means that volumes visible to servers can span multiple partitions or enclosures in the physical storage system. Virtualization provides more flexibility, both during the initial configuration of the system and when expanding storage capacity. For example, an additional shelf of drives can be plugged in, the storage formatted, and the available storage allocated to new or existing volumes.
Read more about storage in InfoWorld's Storage Channel.